Dynamics of electrons and phonons in semiconductors. II. Drag effects

We present an analysis of the dynamics of the coupled electron-phonon system in the presence of an intense electric field in nondegenerate semiconductors. The effects of mutual electron-phonon drag are taken into account. The electron and phonon distribution functions are both assumed to be anisotropic, the isotropic part of the electron distribution being a Maxwell-Boltzmann distribution with a time-dependent electron temperature $T_e\mathrm{}\left(t\right)\mathrm{}$. Comparison is made with the results obtained in neglecting the anisotropy of the distribution functions. It is shown that the anisotropy of the electron and phonon distributions does not drastically change the qualitative evolution of the isotropic part of these distributions; the quantitative differences are functions of the carrier concentration. The stimulated emission of phonons is discussed.